Thread-trimming mechanism for sewing machines



D. G. SMITH ET AL THREAD-TRIMMING MECHANISM FOR SEWING MACHINES Y 4Sheets-Sheet 1 Filed Nov. 14, 1947 INVENTORS @arwin G. Smith and .HaroldC(Fvwlkner ATTORNEY 4 Sheets-Sheet 2 INVENTORS ATTORNEY Darwin GTSmitkand, Jlarold GfiauZkz zer Nov. 8, 1949 D. G. SMITH El AL THREAD-TRIMMINGMECHANISM FOR SEWING MACHINES Filed Nov. 14, 1947 1:). 6. SMITH ET AL2,487,389

THREAD-TRIMMING MECHANISM FOR SEWING MACHINES 4 Sheets-Shet 3 NOV. 8,1949 Filed Nov. 14, 1947 1 N V EN TORS .fiarwin, G. Smith and By HaroldC'- Faulkner WI TNESS: fl ATTORNEY Nov. 8, 1949 D. G. sM H r AL 42,487,389

THREAD-TRIMMING MECHANISM FOR SEWING MACHINES Filed Nov. l4, 1947 4Sheets-Sheet 4 JIIIA'IIIIII. l

' 1N VEN TORS @arwz'n 6'. Smith and WITNESSI: By Jfaz old C(Fzwlner ATTORNE' Y Patented Nov. 8, 1949 H I I 2,487.389

UNITED STATES PTENT OFFICE THREAD-TRIMM'ING MECHANISM FOR SEWINGMACHINES Darwin G. Smith and Harold C. Faulkner, Bridgeport, Conn.,assignors to The Singer Manufacturing Company, Elizabeth, N. J acorporation of New Jersey 1 Application November 14, 1947, Serial No.786,016

Claims. (112252) 1 2 This invention relates to sewing machines and Fig.'7 is an enlarged vertical sectional View more particularly tothread-trimming mecha taken substantially along the line 1--l, Fig. 2,

nisms for machines of the group-stitch type, showing the needle-threadjust after it has been such as tacking machines, button-hole machines,severed with the beginning end of the needleeyelet machines, etc. threadnipped for the beginning of the subsequent The invention aims to improvethe thread-trimstitching cycle. ming and -nipping mechanism disclosed inthe In the preferred embodiment of the invention,

U. S. patent of A. R. Wood, No. 1,920,944, dated the eyelet machineillustrated in the drawings Aug. 1, 1933, so that after the thread hasbeen ompri a fr m in n a bed it uppor n cut and the beginning end of thethread nipped a standard I! of an overha in e -arm the work-clamps maybe opened to release the 12 terminating in a head l3. Mounted in thework without causing any inadvertent shift of e d 3 is t e usualreciprocatoly needle-bar the nipping blade which would prematurely re- Mcarrying a needle I5 which, together with the lease the nipped end ofthe thread, regular under-thread mechanism mounted with- Another objectof the invention is to provide 15 in the bed i0, constitutes thestitch-forming mechactuating mechanism for the trimmer-blade conanism-This mechanism is adapted turnedstructed so that it will not encroachupon th abouta vertical axis to disperse the stitches aboutwork-clearance space beneath the work-clamp the eyelet he Stitch-formingmechanism' is arms and will not interfere with the movement 0 drivenfrom the main sewin S 56 Wh of the Work-clamp into and out ofwork-clamping iv s its power m a us y running position. belt-drivenpulley H. The period of operation With these nd other Objects in view,as will of the stitch-forming mechanism is controlled by hereinafterappear, the invention consists in the the usual Start" and Stop-motionce including thread-trimming and -nipping device described e t lStop-motion v l8 Which, When 1 in connection with the accompanyindrawings erated effects the coupling of the main-shaft it to whichillustrate a preferred embodiment of the the pulley invention and inwhich: As fully explained in the U. S. patent of E. B.- Fig. 1 is aright side elevational View of an eye- Allen. dated y 1920, there is letmachine embodying the invention, portions incorporated in the machinethe usual eyeletu of the machine being broken away. ter shaft It whichmakes one revolution prior to Fig. 2 is an enlarged top plan view ofportions Sewing and en comes to rest, and a Second of the work-clamp andof the machine-frame, auxiliary shaft 20 which is stationary dur theshowing the actuating mechanism for imparting Operation of e Shaft 59and main-Shaft 95 and the required thread-trimming and -nipping makesone revolution after the sewing is commotions to the trimmer. pleted, toperform certain desired operations after Fig. 3 is a plan View of thefeed-wheel, together Stitching, Such as t p ning of the work-clamp. witha portion of the mechanism for rapidly rotatand the rapid drive of thefeed-wheel 2| to restore ing the feed-Wheel at the end of the sewingoperit to initial position. These shafts l9 and 28 are ation, and thatpart of the thread-cutter mechadriven from a Continuously unningbelt-pulley nism actuated by the feed-wheel reversing mech- 1? through ub y Co t o o u o anism. clutch-devices, as fully explained in the aboveFig. 4 is a top plan view of a portion of the mentioned Allen Patent No.1,346,102. right hand work-clamp section, showing the For a clearunderstanding of the present in thread-trimming blade in set positionpreparatory vention it will'be sufiicient to explain that, to to theretrimming of the beginning end of the rapidly drive the feed-cam 2|,the second auxilneedle-thread. iar shaft 20 is formed with a crank 23which Fig. 5 represents a vertical section taken subis connected by apitman 24 to an arm 25 mlstantially along the line 55, Fig. 2, showing,in crumed coaxially with the feed-wheel and piv dotted lines, theposition of the parts when the i thread-trimming blade is open and,infull lines, spring 21 (Fig. 1) to ride on the-periphery of the otallycarryin a pawl 26 whichisurged by a the position of the parts when thethread-trimfeed-cam and acts upon a tooth 28 onthe feed-- ming blade isclosed. wheel during the single rotation of the crank 23;

Fig. 6 is an enlarged vertical sectional view rapidly turnin thefeed-wheel at one sweep fromv taken substantially along the line B-6,Fig. 2. its position at the end of a sewing operation to initialposition ready to begin a new cycle of operations.

The work is adapted to be held in a workclamp during the sewingoperation. The workclamp which is shown in the drawings forms thesubject of pending application Serial No. 786,014, filed Nov. 14, 194'?in the name of H. C. Faulkner, and includes lower clamp-plates 23, 36and opposed upper clamp-feet 3|, 32. The clamp-feet are pivotallyfastened by means of pivot-screws 33, 34 to the free ends of the archedclamp-arms 35 and 36, each of which is fulcrumed at its rear end on ahinge-pin 31 provided .in;a supporting bracket 38, only the bracket forthe clamp-arm 35 being shown in the drawings. The clamp-foot 3| isyieldingly held against the work, when the work-clamp is closed, by acoil-spring 39 which is interposed between the arm 35 and a thumbnut 40threaded on a pull-rod 4|. As fully shown and described in the pendingapplication above referred to, thereis provided suitable togglemechanism connected .Withthe pull-rod 4| for effecting the closing andopening of the work-clamp. The clamp-arms 35, 36 are appreciably archedand the fulcrum supports for said arms are disposed considerably backfrom the feet 3|, .32 in order to provide ample work-clearance spacebeneath the arms.

The needle-thread trimming and -nipping mechanism now to bedescribed-comprises a trimmer-blade 42 and .an overlying nipper-blade 43(Figs. 4, and '7), the shanks of which are secured to the lower end ofthe usual vertical rockshaft 44 journaled in the clamp-foot 3|. Thisconstruction is substantially the sameas that disclosed in the U. :S.patent of E. B. Allen, No. 885,310, dated April '21, 1908. Thethread-trimming and nipping blades 42 and 43 are adapted tooperate inahorizontal slot defined between a section 45 of the clamp-foot 3| (Figs.6 and 7) and the surface of a hardened detachable section 46 secured tothe clamp-foot 3|. The nipperblade 43 cooperates with the section 45 asshown in Fig. 7 to hold the beginning end of the thread during thesewing of the first portion of the eyelet. The trimmer-blade 42 has asharpened edge which cooperates with an edge on the detachable section46 in severing the needle-thread.

The'trimmer-blade carrying rock-shaft 44 has fixed .on its upper end arock-arm 41 connected by a link 48 to a rock-lever 49 freely pivoted ona'stud 50 threaded into the clamp-foot 3|. Depending from the rock-lever49 is a ball-stud 5| embraced by .the socketed front end of an actuatinglink 52 arched in substantial conformity with the clamp-arm 35 (Fig. 1)and connected at its rear end to the upper end of a trimmer-openinglever 53 pivoted intermediate its ends on a stud 54 threaded into thesupporting bracket 33. Rising from the upper end of the trimmeropeninglever 53 is a projection 55 to which is attached one end of acoil-spring 56 connected at its other end to an ear 51 secured to theclamparm 35, the coil-spring acting to bias the trimmeropening lever 53into trimmer-blade closed position determined by a buffer pad 58 securedto the trimmer-opening lever 53 contacting an upstanding stop 59provided on the clamp-arm 35. As will be seen in Figs. 2, 6 and '7, whenthe trimmerand nipper-blades 42 and 43 are in closed position. thecenter of the ball on the ball-stud 5| is disposed in alinement with thelongitudinal axis of the pivot-screw 33. It will be appreeiated thatwhile this alined position of the balleand-socket joint of the link 52with the pivot-screw 33 is maintained, any tilting of the clamp-foot 3|about the axis of the pivot-screw 33 while the work-clamp is opened willnot cause the trimmerand nipper-blades 42 and 43 to shift in the slot inthe clamp-foot 3|. Obviously, since no accidental shift in the blade 43occurs the beginning end of the thread is held securely regardless ofwhether the clamp-foot 3| is tilted about the pivot-screw 33 during theinsertion or removal of work ,from the opened work-clamp.

The thread-trimming and -nipping blades are adapted to be operated twicefor each complete stitching cycle, once before the sewing is completedto retrimt-he beginning end of the needlethread, the operation beingperformed preferably after the sewing has progressed to the point wherethe beginning endcannot be sewed in or bound down by the stitching, anda second time after the sewing is completed to cut the needle-threadclose to the work and hold the beginning end of the needle-thread forthe beginning of the next sewing operation. A thread-trimming mechanismhaving substantially the same sequence of operations is disclosed, forexample, in the U. S. patent of A. R. Wood, No. 1,839,823,.issued Jan.5, 1,932. In-the present case, the first or retrim operation isperformedby meansactuated by the feed-cam 2|. This means preferably comprises avertically disposed rock-shaft 66 journaled in the bed 56 and havingattached to its lower end an arm 6| having its inner end underlying thefeed-cam and disposed to be engaged by a retrim-cam 62 attached to theunder side of the feed-cam 2|. Secured to the upper end of therock-shaft 66 is a rock-lever 63 provided at its outer end with a slot64 disposed to receive a screw 65 threaded into a push-lever 66fulcrumed at one end on a pivot-stud 61. The free end of the push-lever66 is arranged to swing into engagement with the lower end of thetrimmeropening lever 53. A spring 68 bears against the push-lever 56 andurges itinto an inoperative position determined by a stop-pin 66. Fromthe above description considered in connection with Figs. 2 and 4, itwill be understood that as the feed-cam 2| turns in the direction of thearrow in Fig. 2, the retrim-cam 62 contacts the free end of the arm 6|which swings it in a counterclockwise direction, transmitting to thepush-lever 66, through the rock-shaft 60 and rock-lever 63, movement ina counterclockwise direction also. This movement of the push-lever 66turns the trimmer-opening lever 53 from the full line position in Fig. 5to the dotted line position. This turning of the trimmer-opening lever53 gradually moves the trimmerand nipper-blades 42 and 43 into an openposition, shown in Fig. 4. In swinging from closed or thread-nippingposition to open position, the beginning end of the needlethread isreleased .and the trimmer-blade is set for its retrim stroke. As thefeed-cam 2| continues to turn. the retrim-cam 62 advances to a pointwhere its drop-off passes the end of the arm SI and when this occurs thecoil-spring 56 snaps the link 52 ina direction to close thetrimmar-blade 42 upon and retrim the beginning end of the needle-threadclose to the work. The spring 68 acts simultaneously with thecoil-spring 56 in returning the push-lever 66 and its associatedconnections to their inoperative position.

To provide for reopening or resetting the trimmer-blade 42 preparatoryto the trimming of the finishing end of the needle-thread (Fig. 7) andnipping the beginning end of the needle-thread for the beginning of thenext sewing operation,

we have provided a second means actuated by the single rotation of theauxiliary shaft for operating the rock-shaft 60. This means preferablycomprises a rock-arm Ill (Figs. 1 and 5) secured to the rock-shaft 60and extending substantially horizontally immediately above the level ofthe feed-cam 2|. At its free end the rock-arm I0 is formed with adownturned lip II providing on its inner face a straight cam-wall I2extending in a direction inclined to and extending across the path oftravel of the feed-cam turning pawl 26. The pawl 26 is provided with anupstanding pin I3 which is disposed so that, as the pawl 26 is actuatedby the pitman 24 to effect the rapid turning of the feed-cam 2| afterthe stitching operation is completed, the pin I3 will strike the camwallI2 and swing the rock-arm Ill in a counterclockwise direction and intothe position shown in Fig. 3. With the parts in the position shown inFig. 3, the trimmerand nipper-blades 42, 43 are open or reset. As thepawl 26 continues in its feed-cam turning stroke, the pin 13 travelsbeyond the end of the rock-arm I0, permitting the spring 56 to snap thetrimmerand nipperblades 42, 43 into closed position, whereby the threadis cut and the beginning end nipped (Fig. '7). The spring 68 returns therock-arm Ill and its associated connections to the position illustratedin Fig. 2. When the crank 23 on the auxiliary shaft 20 travels throughthe second half of its single revolution, the pawl 26 is returned to itsinitial position in readiness for its operation at the end of the nextstitching cycle. During the return stroke of the pawl 23 to its initialposition the pin I3 on said pawl strikes the outside face of thedownturned lip II, causing the pawl 28 to turn in opposition to thespring 21 on its pivotal connection with the arm 25, the spring 21biasing the pawl back so that its toe rests on the periphery of thefeed-cam 2| after the pawl passes the back end of the downturned lip II.

It will be appreciated from the foregoing that we have invented aneedle-thread trimmer and nipping device constructed so that thenipperblade is not accidentally shifted and the beginning thread-endreleased by the tilting of the work-clamping foot on its pivotal supportduring the insertion or removal of Work or during the traversing of anyunevenness in the material due to cross-seams or the like. Moreover, theactuating mechanism for the trimmer and nipping device is arranged sothat ample clearance space is provided beneath the work-clamping feet topermit convenient manipulation of the work and to permit the placing ofthe stitched pattern back from the edge of the work. Also the actuatingconnections are designed so that they will not interfere with themovement of the work-clamp into and out of work-cutting position, andthe position of the pivot 54 of the trimmer-opening lever 53 relative tothe hinge pin 31 of the clamparm 35 is such that during the opening andclosing of the work-clamp the bufier pad 58 slides up and down on theface of the stop-lug 59 in a direction substantially normal to the axisof the link '52. Thus, no endwise movement is imparted to the link 52during the opening and closing of the work-clamp and consequently thetrimmerand nipper-blade is not disturbed.

Having thus set forth the nature of the invention, what we claim hereinis:

1. A group-stitch sewing machine having a work-clamp provided with anupper clamp-foot pivotally mounted for tilting movement about afulcrum-axis, a thread-trimmer and -nipper device carried by said upperclamp-foot, and actuating' mechanism for operating said thread-trimmerand -nipper device; said mechanism including a pair of elements carriedby said work-clamp and a ball-and-socket connection between'saidelements with the-center of the balldisposedin alinement with thefulcrum-axis of said clampfoot when said thread-trimmer and -nipperdevice is closed.

2. A group-stitch sewing machine having a work-clamp provided with anupper clamp-arm, a bracket to which said clamp-arm is pivoted, aclamp-foot mounted on one end of said clamparm for tilting movementabout a fulcrum-axis, a thread-trimmer and -nipper device carried bysaid clamp-foot, and actuating mechanism for operating saidthread-trimmer and -nipper device, said actuating mechanism including arocklever pivoted on said clamp-foot, a trimmeropening lever fulcrumedon said bracket, a link connected at one end to said rock-lever and atits other end to said trimmer-opening lever, the point of connectionbetween said link and rocklever being in alinement with the fulcrum-axisof the clamp-foot when said thread-trimmer and -nipper device is closed,and means for operating said trimmer-opening lever.

3. A group-stitch sewing machine having a work-clamp, provided with anarched upper clamp-arm, a bracket to which one end of said clamp-arm ispivoted, a clamp-foot mounted on the other end of said clamp-arm; athreadtrimmer and -nipper device carried by said clamp-foot, andactuating mechanism for operating said thread-trimmer and -nipperdevice, said actuating mechanism including a rock-lever pivoted on saidclamp-foot and operatively associated with said thread-trimmer and-nipper device, a trimmer-opening lever pivoted on said bracket adjacentthe pivotal support of said clamp-arm, a link shaped to conformsubstantially with the arched clamp-arm and connecting saidtrimmer-opening lever to said rock-lever, and automatically controlledmeans for operating said trimmer-opening lever.

4. A group-stitch sewing machine having stitch-forming mechanism, afeed-cam for effecting the distribution of stitches in a given pattern,feed-cam rapid-turning means for returning the feed-cam to its initialposition after the stitching is completed, a thread-trimmer and -nipperdevice, and means for actuating said device twice for each completestitching cycle, said means including a rock-shaft, means operativelyconnecting said rock-shaft to said thread-trimmer and -nipper device, areset cam on said feed-cam, a rock-arm secured on said rock-shaft anddisposed for engagement by said reset cam to effect one of theoperations of said thread-trimmer and .-nipper device, and a secondrock-arm secured to said rock-shaft and arranged for engagement by saidfeed-cam rapid-turning means for efiectin the other operation of saidthread-trimmer and -nipper device. 1

5. A group-stitch sewing machine having a work-clamp provided with anupper clamp-arm, a clamp-foot mounted on said clamp-arm for tiltingmovement about a fulcrum-axis, a threadtrimmer and -nipper devicecarried by said clamp-foot, and actuating mechanism for operating saidthread-trimmer and -nipper device, said actuating mechanism including atrimmer-carrying rock-shaft, a rock-arm secured to said rock-shaft, arock-lever pivoted on said clampfoot, a link connecting said rock-arm tosaid IQOKFIQYBI', a second link connected to said rock- REFERENCESCI'IIEI) 16V?! afipomt m ahnement wi fulcruim' The following referencesare of record in the axis of; said clampriootwhen, said thread-trimfilethis patent,

merand -nipper device is. in closed position, and I operating mechanismconnected to said second 5 UNITED STATES PATENTS link. Number Name DateDARWIN SMITH- 1,066,862 Sullivan July 8, 191 3 HAROLD C. FAULKNER.

